1. Field of the Invention
This invention relates to a fluid actuated pump system and more particularly to a rotary control valve for controlling the flow of fluid under pressure alternately to opposite faces of a piston to generate reciprocating movement of the piston.
2. Description of the Prior Art
Hydraulically-actuated pumps are well known in the art and generally include two types, the double acting piston type and the single acting plunger type. The double acting piston type includes a piston positioned for reciprocal movement in a cylinder. As the piston moves in one direction, fluid is discharged from one end of the cylinder while fluid enters the opposite end of the cylinder. Then when the piston moves in the opposite direction, the fluid is discharged from the opposite end of the piston while fluid enters the other end of the cylinder. With a single-acting plunger pump, however, fluid is moved or delivered on the forward stroke only.
U.S. Pat. No. 3,022,738 discloses a pump system for supplying and controlling hydraulic fluid under pressure to hydraulic motors coupled to pistons or plungers in a pump mechanism. The velocity of the fluid being pumped or discharged by the pistons is controlled at a constant velocity in order to eliminate pressure surges. The pump system utilizes a hydraulic control valve which includes a rotating cylinder having a plurality ports through which fluid is displaced in various rotational positions of the rotating cylinder. The hydraulic control valve receives a constant volume of fluid and is operable to meter the hydraulic fluid to hydraulic cylinders which control the acceleration and deceleration of hydraulic pistons that drive a pump for pumping fluid.
U.S. Pat. Nos. 3,547,206 and 3,654,961 disclose in a rotary percussion drill a multivalve control device that includes a plurality of individual pressure and vent valves connected in a stacked arrangement. The pressure and vent valves alternately supply fluid under pressure to opposite sides of a reciprocating piston within a cylinder. A timing device is drivingly connected to shafts of the valve members of the pressure and vent valves. The timing device is operable to open and close the pressure and vent ports to supply the pressurized fluid alternately to the opposite sides of the piston.
While it has been suggested by the prior art system to provide control valves for metering the flow of pressurized fluid to a double acting positive displacement pump or to opposite sides of a reciprocating piston within a cylinder, the prior art devices are unduly complex requiring many components that are not suitable for mounting in compact arrangements. This is of particular importance in underground mining operations where the work area is extremely limited and the operating machinery must be compactly designed for efficient operation.
Thus there is need in underground mining operations for a fluid actuated pump system capable of efficient operation on a mining machine or any other suitable piece of equipment in the mine for generating a water spray to suppress the circulation of dust particles in the working atmosphere and particularly at the mine face when the mine material is being dislodged.